1. Field
One or more embodiments of the present invention relate to a secondary battery.
2. Description of the Related Art
Secondary batteries have been esteemed as power sources for a variety of electronic and communication devices as they are rechargeable and portable.
In typical secondary batteries, an electrode assembly, having electrode plates and separators that are alternately stacked and selectively rolled up, is mounted in a case. An electrode tab is attached to the respective electrode plates of the electrode assembly. When the electrode assembly is mounted in the case, an end portion of the electrode tab protrudes out of the case and is electrically connected to an electrode lead.
The case is designed such that an edge thereof, except for a portion through which the electrode tab protrudes, is sealed. At this point, although a sealing film is interposed between the case and the electrode tab, a rate of defective products caused by an electrolyte leak or a gas leak is still high.
In addition, the protruding end portion of the electrode tab is coupled to the electrode lead and takes up a separate space. That is, the electrode tab and the electrode lead extend by a length to be capable of being welded to each other, and thus a separate space, in which the electrode tab and the electrode lead that are welded to each other can be disposed, is required. For a high capacity battery, the separate space takes up about 15-30% of the space of the battery pack. Therefore, the structure where the electrode tab and the electrode lead are coupled to each other at an external side of the case causes the capacity of the battery to be reduced.
Furthermore, the electrode tab and the electrode lead are coupled to each other by welding. The welding portion may easily contact other components or may be easily damaged by external impacts. This causes the battery to be defective.